DIAGNOSIS The thermal overload protector tripped. The motor overheated from a dull chain or pushing too hard.
FIX Let the saw cool down for 15-20 minutes. Sharpen the chain. Do not force the saw, let the chain speed do the work.
IF THAT DIDN'T WORK Check the battery contacts on the saw. Look for green corrosion. Clean them with a pencil eraser or fine grit sandpaper.
HEADS UP A sharp chain prevents 90% of performance issues. If it's making sawdust, not chips, it's dull.